Document annotation is a powerful tool for, among other things, emphasizing particular portions of a document, helping to summarize longer text passages of a document, and showing connections among different portions of a document. Conventionally, readers of a paper document might highlight a passage of the document, make notes in the margins of the document, or circle, underline or place an asterisk next to selected passages of the document. These types of markings are typically added to a document that has already been completed by a given author. The reader of the document may then subsequently make markings on the document for his own personal use, or for the benefit of others.
Document annotation with electronic documents, e.g., those stored in a memory of a computer system and displayed on a computer screen for viewing, has seen increased acceptance in the recent past. For example, word processor software such as Microsoft Word™ (Redmond, Wash.) allows users to highlight and underline selected text, and even to “attach” comments at selected locations within a document. When a pointing device, such as a mouse, passes over the selected location to which a comment has been attached, a comment “bubble” might be displayed. The bubble might then subsequently disappear when the mouse is moved away from that location.
Similarly, Adobe Acrobat™ provides built-in document annotation functionality. Given a document stored in accordance with Adobe's PDF standard, Acrobat provides a plurality of possible commenting and marking-up annotation tools, including highlighting, text bubbles and call-outs. In addition, Acrobat provides the ability to place various shapes such as circles, arrows and lines on the PDF document. These annotations can also be saved with the original PDF document.
While the Microsoft Word™ and Adobe Acrobat™ approach to document annotation can be very powerful in that one's own markings can be relatively easily introduced into a document, the types of annotations that are possible within computer software applications such as Word and Acrobat are limited or, more precisely, are limited to specific functionality that is already or pre-built into the given software application. As such, the types of available annotations are, in effect, predetermined. Consequently, there remains a need for more expansive forms of document annotation.